The present invention relates to coated abrasive discs and to an economical method of making coated abrasive discs adapted for easy modification to meet specific requirements.
Traditionally abrasive discs comprise a substrate which may be made of polymer film, paper, or a knit, woven or stitch-bonded fabric. The backing may need to be "filled" to ensure that a binder applied thereto does not become absorbed into the material. This may be referred to as a "size" and may be applied to the front, back or both sides. A binder, called the "make" coat, is applied to the backing and before the binder is cured, abrasive grits are applied to the binder and the binder is then cured to anchor the grits in place. A second binder layer also, (perhaps confusingly), called a "size" coat, is usually applied over the grits to complete the anchoring of the grits.
In conventional manufacturing the above process is applied to a continuous sheet and the individual discs are punched out from a large roll of the sheet, called a "jumbo". Even with the closest possible spacing of the punched out shapes, there is a significant amount of waste in terms of backing, abrasive grain applied and binder used to anchor the grain. The larger the disc diameter, the larger the amount of waste. In addition the production method requires that the disc have a uniform construction at all points since the same jumbo may be used to produce discs of various diameters and even belts.
However, the way an abrasive disc is conventionally used, only the outside edge of the disc is actually used before the disc is considered worn out because of the angle at which the disc is presented to the workpiece. Thus the usual methods of making the discs is wasteful as made from a jumbo and as used in practice.
The present invention provides a means of making abrasive discs more economically and this leads to the possibility of making novel abrasive disc structures that can be designed to provide significant advantages over the prior art.